Question

Qual a massa, em gramas, de 15.10^23 moléculas de h2o?

Answer 1

$\Large\boxed{\begin{array}{l}\sf m_{H_2O}=2\cdot1+16=18\,g/mol\\\sf 18\,g\longrightarrow 6\cdot10^{23}\,mol\acute eculas\\\sf x\longrightarrow 15\cdot10^{23}\,mol\acute eculas\\\sf 6x=18\cdot15\cdot10^{23}\\\\\sf x=\dfrac{\diagdown\!\!\!\!\!\!18\cdot15\cdot10^{23}}{\diagdown\!\!\!\!6}\\\sf x=3\cdot15\cdot10^{23}\\\sf x=45\cdot10^{23}\\\sf x=4,5\cdot10^{24}g\end{array}}$